This invention relates to asphalt emulsions and emulsifiers used in preparing asphalt emulsions.
In the manufacture of pale wood rosin from southern pine stumpwood, crude rosin is extracted from the wood and then refined using solvent/solvent partitioning between aliphatic hydrocarbon and polar solvents. One of the by-products of this operation is a dark, high melting, largely aliphatic hydrocarbon-insoluble resin, hereinafter referred to as AHI resin. AHI resin is a thermoplastic resin that chemically is a complex mixture of high molecular weight phenolic compounds, rosin acids, neutral materials and several minor components. An AHI resin is produced as described in U.S. Pat. No. 2,221,540, which patent is incorporated herein by reference in its entirety. A preferred AHI resin is Vinsol(copyright) resin available from Hercules Incorporated, Wilmington, Delaware.
AHI resin, particularly Vinsol(copyright) resin from Hercules Incorporated, Wilmington, Del., is used in a wide variety of industrial applications including asphalt emulsions. Asphalt emulsions are used in a variety of applications such as road building, road sealing, soil stabilization, mulching, surface coating of asphalt pavements, and built-up roofs. Because the amount of wood rosin produced relative to tall oil and gum rosin is declining, the supply of AHI resin available for industrial applications is also declining. Consequently, there is a need for a material which will perform in asphalt emulsions in a manner similar to AHI resin.
U.S. Pat. No. 5,656,733 describes resinous compositions comprising lignin and polymerized rosin, and the use of such compositions as asphalt emulsifiers and air entraining agents for concrete.
This invention pertains to asphalt emulsions containing an emulsifier comprising an alkali metal or ammonium salt of solidified pyrolytic wood tar oil.
In another embodiment the invention comprises a resinous composition comprising a first component selected from the group consisting of solidified pyrolytic wood tar oil and salts thereof, and a second component selected from the group consisting of rosins and salts thereof.
In yet a third embodiment the invention pertains to a method for preparing a resinous composition comprising: combining solid ingredients comprising solidified pyrolytic wood tar oil and a rosin selected from the group consisting of natural rosin, fortified rosin, polymerized rosin, hydrogenated rosin, disproportionated rosin, modified rosin and esterified rosin; and milling the combined solid ingredients until a substantially homogeneous particulate blend is obtained.
In yet another aspect, the invention pertains to a method for preparing an asphalt emulsion comprising dissolving ingredients comprising a rosin and solidified pyrolytic wood tar oil in an aqueous solution of alkali metal or ammonium hydroxide in water to form an aqueous solution of emulsifier, mixing the aqueous solution of emulsifier with asphalt to form a mixture, and milling the mixture to form an emulsion of the asphalt.
Solidified Pyrolytic Wood Tar Oil
The solidified wood tar oil for use in the current invention is produced by thermal destructive distillation, for example fast pyrolysis of biomass, e.g., wood. The controlled, rapid heating of the biomass material (e.g., wood) initiates depolymerization reactions in the lignin component while minimizing condensation reactions. In addition, the very short reaction times and rapid vapor quench employed in fast pyrolysis preserve the lignin polymer fragments by protecting them from prolonged exposure to high temperatures. In summary, the high intensity but very short xe2x80x9cthermal shockxe2x80x9d of fast pyrolysis causes the lignin component of the wood feedstock to depolymerize, yielding reactive polymer fragments in a molecular size range suitable for subsequent controlled crosslinking. Fast pyrolysis processes are described in U.S. Pat. Nos. 4,876,108; 5,792,340; 5,853,548 and 5,961,786, all of which are incorporated herein by reference in their entireties.
The rapid destructive distillation or fast pyrolysis involves the rapid heating of biomass material. Reaction temperatures of 500xc2x0 to 550xc2x0 C. allow maximization of the production of desired product vapors while minimizing byproduct gas and char. The product vapors are rapidly condensed and collected. This product, referred to as whole oil, bio-oil or pitch is used as a feedstock for further processing to produce solidified pyrolytic wood tar oil.
The subsequent processing of the whole oil involves the non-destructive distillation and evaporative treatment of the material. The non-destructive techniques for distillation-evaporation include wipe film evaporation, roto-evaporation, agitated film evaporation, vacuum distillation, falling film, etc. These non-destructive techniques remove or reduce the content of water, acids, odors and non-resin components by heat and/or vacuum distillation. In addition, the carefully controlled temperatures used during evaporation allow a controlled polymerization of the feedstock to occur while maintaining the reactive sites in the final product. In summary, distillation/evaporation can be controlled to product an optimized degree of crosslinking or polymerization, resulting in a solidified pyrolytic wood tar oil.
In the case of the solidified pyrolytic wood tar oil for this invention, the distillation/evaporation conditions are controlled to produce product with the following preferred property ranges: softening point (Fisher-Johns), from about 100xc2x0 to about 170xc2x0 C.; acid number, from about 10 to about 50; glass transition temperature (Tg) of from about 30xc2x0 to about 100xc2x0 C.; weight average molecular weight (size exclusion chromatography) of from about 1,500 to about 4,500; and number average molecular weight of from about 500 to about 1,000. More preferred property ranges are: softening point, from about 140xc2x0 to about 160xc2x0 C.;
acid number, from about 20 to about 30; glass transition temperature (Tg) of from about 70xc2x0 to about 100xc2x0 C.; weight average molecular weight (size exclusion chromatography) of from about 3,000 to about 4,000; and number average molecular weight of from about 750 to about 1,000.
Preferably, the solidified pyrolytic wood tar oil will contain from about 40% to about 60% of material of number average molecular weight less than about 1,000, and from about 20% to about 30% less than about 500.
Rosins
The rosins useful for the present invention can be any thermoplastic rosin, including unfortified rosin, fortified rosin, extended rosin, rosin esters, acid modified rosin esters, polymerized rosin, dimerized rosin, disproportionated rosin, hydrogenated rosin, hydrogenated rosin esters and mixtures and blends thereof. Preferred rosins for use in the invention are fortified rosins and polymerized rosin.
The rosin used in this invention can be any of the commercially available types of rosin, such as wood rosin, gum rosin, tall oil rosin, or mixtures of any two or more in their crude or refined state. Partially hydrogenated rosins and polymerized rosins, as well as rosins that have been treated to inhibit crystallization, such as by heat treatment or reaction with formaldehyde, can also be employed. Rosins for the invention preferably will have an acid number of at least about 100, more preferably at least about 150, and most preferably at least about 200.
Fortified rosin useful in this invention is the adduct reaction product of rosin and an acidic compound containing the 
group and is derived by reacting rosin and the acidic compound at elevated temperatures of from about 150xc2x0 C. to about 210xc2x0 C.
The amount of acidic compound employed will be that amount which will provide fortified rosin containing from about 1% to about 16% be weight of adducted acidic compound based on the weight of the fortified rosin. Methods for preparing fortified rosin are well known to those skilled in the art. See, for example, the methods disclosed and described in U.S. Pat. Nos. 2,628,918 and 2,684,300, the disclosures of which are incorporated herein by reference.
Examples of acidic compounds containing the 
group that can be used to prepare the fortified rosin include the xcex1,xcex2-unsaturated organic acids and their available anhydrides, specific examples of which include fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride and acrylic acid. Mixtures of acids can be used to prepare the fortified rosin if desired. Thus for example, a mixture of the acrylic acid adduct of rosin and the fumaric acid adduct can be used in the invention. Also, fortified rosin that has been hydrogenated after adduct formation can be used.
For use in the present invention fumaric acid and maleic anhydride are preferred, and fumaric acid is most preferred. When fumaric acid is employed as the fortifying agent, the preferred amount of fumaric acid employed will be that amount which will provide fortified rosin containing from about 1% to about 16% by weight of combined or adducted fumaric acid based on the weight of the fortified rosin. More preferably, the amount employed will provide fortified rosin containing from about 1% to about 10% by weight of adducted fumaric acid, and most preferably from about 1 % to about 5% by weight fumaric acid.
Various rosin esters of a type well known to those skilled in the art can also be used in the present invention. Esterified rosins comprise esters formed from any of the above mentioned rosins and an alcohol. Suitable exemplary rosin esters may be rosin esterified as disclosed in the U.S. Pat. Nos. 4,540,635, and 5,201,944, the disclosures of which are incorporated herein by reference. Suitable alcohols include polyhydric alcohols such as ethylene glycol, glycerol, diethylene glycol, triethylene glycol, pentaerythritol, 1,4-butanediol, sorbitol, and mannitol, aminoalcohols such as triethanolamine, triisopropanolamine, and tributanolamine, and polyethylene and polypropylene glycols.
Polymerized rosin useful in this invention is manufactured by acid catalyzed polymerization of rosin. It comprises predominantly dimeric rosin acids and is generally available as a mixture of dimerized and monomeric rosin acids. Commercially available polymerized rosin comprises a mixture of about 30 to about 90 wt. percent rosin dimer and about 10 to about 70 wt. percent rosin acids. The preferred polymerized rosin for this invention comprises a mixture of from about 30 to about 50 wt. percent dimerized rosin. The most preferred polymerized rosin is Poly-Pale(copyright) resin available from Hercules Incorporated, Wilmington, Del.
The asphalt emulsions of this invention contain an emulsifier comprising an alkali metal or ammonium salt of solidified pyrolytic wood tar oil. Preferably, the emulsifier will further comprise an alkali metal or ammonium salt of a rosin as described above, preferably fumaric acid fortified rosin or polymerized rosin. The asphalt emulsifiers are generally used at a level of from about 1 to about 2 weight percent based on the total weight of the emulsion.
In the preferred case, i.e., when an alkali metal or ammonium salt of a rosin is used together with solidified pyrolytic wood tar oil, the ratio of solidified pyrolytic wood tar oil to the rosin or mixture of rosins on a weight basis is from about 1:3 to about 3:1. Preferably the ratio is from about 1:2 to about 2:1, and more preferably from about 1:1.5 to about 1.5:1.
A preferred method for preparing the resin composition for use as an asphalt emulsifier comprises blending and mixing the solidified pyrolytic wood tar oil, the rosin or rosins, as well as any additional ingredients, in the form of lumps, flakes or powders, followed by grinding or milling the ingredients under conditions ensuring good mixing until a homogeneous mixture is obtained. Any high shear mixers suitable for blending solids are usable for this purpose. The resin composition prepared in this way may be converted into an asphalt emulsifier by solution of the blended composition in aqueous alkali metal or ammonium hydroxide.
Alternatively, the emulsifier may be prepared without the solid blending step by separately dissolving the ingredients in an aqueous solution of alkali metal or ammonium hydroxide to form an aqueous solution comprising a salt.
In most case the emulsifier solution will be used in the form of the aqueous solution. However, if desired, the water can be removed from the aqueous solution to form a solid, substantially dry salt. Preferred methods of water removal are distillation and spray drying.
The alkali metal for use in preparing the emulsifiers of the invention is selected from the group consisting of lithium, sodium and potassium. The preferred alkali metal is sodium.
Thus the resinous compositions of this invention may be in free acid form, in the form of a salt of an alkali metal or ammonium, or as mixtures of both. In the free acid form, properties of the compositions which are usually measured are the acid number and the Ring and Ball softening point. In the free acid form, the acid number of the resinous compositions of this invention is preferably from about 100 to about 130, more preferably from about 110 to about 120, and the Ring and Ball softening point is preferably from about 110xc2x0 C. to about 140xc2x0 C. and more preferably from about 120xc2x0 C. to about 130xc2x0 C.
This invention is illustrated by the following examples, which are exemplary only and not intended to be limiting. All percentages, parts, etc., are by weight, unless otherwise indicated.
Materials and Procedures
Softening points of solidified pyrolytic wood tar oil were determined on a Fisher-Johns Melting Point Apparatus. Softening points of all other materials were Ring and Ball softening points, determined by ASTM method E-28(1992). The acid number of a material is defined as the number of milligrams of KOH required to neutralize 1 gram of material.
Solidified pyrolytic wood tar oil: Wood was pyrolyzed at 500-550xc2x0 C. by the methods described in U.S. Pat. No. 5,792,340, which is incorporated herein by reference in its entirety. The bio-oil from the pyrolysis system was then heated at 150-250xc2x0 C. under vacuum in a wiped film evaporator until the product solidified pyrolytic wood tar oil had a Fisher Johns softening point of 130xc2x0 C.
Polymerized rosin: Poly-Pale(copyright) resin, available from Hercules Incorporated, Wilmington, Del. contains approximately 40 wt. % rosin dimer and 60 wt. % monomeric rosin
AHI resin: Vinsol(copyright) resin obtained from Hercules Incorporated, Wilmington, Del., acid number 90-105, Ring and Ball softening point 103-123xc2x0 C.
Fumaric acid adduct of rosin: For preparation of the fumaric acid adduct of rosin, gum rosin was heated to 170xc2x0 C. and then the desired quantity of fumaric acid was added. The resulting mixture was heated to 200xc2x0 C. and stirred for about 2 hours. In the examples presented herein the amount of fumaric acid was 4% by weight of the rosin. The acid number of the product was 196, and the Ring and Ball softening point 97xc2x0 C.